Concrete form lining material



O. W. FROST ET AL CONCRETE FORM LINING MATERIAL Filed May l, 1946 I INVENTOR.: //l www Sept. 2, 1952 y Mg Patented Sept. 2, 1952 rcuttv WjFrost, Highland Park, and James" H.' Conover,A Chicago, Ill.; assgnors to United States 'Gypsum Company,

poration of Il linoisVr 1 Chicago, Ill., a cor- ApplicationMay 1, 1946, Serial No. 666,513

nThe present invention` :concerns 1an improved materialffor'lining'forms suchas rare used concrete'construction. It is, usually, provided in theiorm of `sheets of fiibroustbo'ard from 1/2 inch" inthickness, and upward, provided with a suitablyuabsorbent surface. i i Y l AItis essential that a `material of this kindV have the ability toz absorb "water from 'thefreshly l poured concrete surface' andyet not 4to stick to it asfthe concrete' hardens; l The liningfin absorb-V ing watervfromthe surface, serves twoV purposes.

Itcauses the surface to'be harderand alsotends; toireducesurface voids in the concrete by breaking` any'air bubbles and allowing the concrete toform' asmooth surface against the lining;

crete When'it 'is removed; aftersetting, so that a clean surface is obtained..r l i Several types of form lining material purportf. ingfto serve this purpose areqon the marketgat 13 Claims.`

inthe merest outline, of a process of forming a ber board, showing means `for applying the coating or modifying composition of the present Hinvention; and

Fig.v V2 is a cross section through one of the treated boards, shown in about twice actual size. The ,product of. `thepresent invention is made of` 1/2"` inch insulation board, but is unsized andA 'absorbent-only to' a depth ofaDDQXiinately aas inchloii one surface. The remainder of the board isfwelll sized` andvconsequently remains firm and stiff-fwheniused as a lining, so that rough wood mafyfb'eiised i'riwmaking `the forms. Also, in piles 'orl packages, iii-only the sized water resistant Yl5 The lining must not stick'to the hardened Vcon-f'v "desired absorbency, A board with rapid absorb- *120 the'` present time. One consists or `adilutoiis sheet similar to cardboard,V approximately l/SQ thick anddunsizedsoas Yto give it absorptive properties, havinga large mesh cloth` material,-similarV to'cheesecloth,laminated to it to prevent Vsticking and surface voids'. The other-,type consists of a uber-,insulation board with va reduced amount ofl s'izingto give absorptive properties, having the f surface 'treated' with any vulti-Stic'king Aagentl such as tannicacid.,VIK

Both 'types `0fA material 'have thediSadVantages of becoming soaked throughout'and"unusable exposed to Water before application. Care vmust be taken that lth'eyare not rained onbefore using. All packages and uncovered piles must, therefore, be protected on the job. Y f

Whenused as' a lining, these materials b ecome' soft and flimsy, due toV 'absorbed water and x is then pressedby rollersor thelike', usually beany irregularities in' thev form material, suchV as,

tha-tof roughjvvood,Y leaves aprint on the hard-v enedpOncr'ete'. This makes it necessary to use a high grade-forming material.

It) is one-ofthe Aobjectsofthe Epresent'uiriii/e111.;

tion to "fprovidea `liningV material of relativelyH 1' rigid form, which hasa suitably water-absorbent surface thatf is 'off-such naturefthat ltheset concrete' orfcement 'will not adhrethereto, there# fore, lfermittingclean separationv ofthe for-m from'the resulting concrete or cementstructure.

Afrtherfobjeot ofthe presentinvention is" to provide process for-.the production of such `a concretef-formlining material.

rlhe invention is illustrated by two figures, of

which; r V t Fig. 1 is a. purely diagrammatic representation,

surfaceis exposed, there is. much :lessV danger. Y

froiriA exposure 4tol water- .v .Also in production of the fiber boards 'known to the art the degree of sizing Ymust be carefully controlled to give the ency is not suitable, as it draws the water too rapidly'fm the surface of the concrete. Such controlof the degree of sizing is extremely diicult.

The iiberinsulation boardof the present invention isv made' bythe method known tothe artasV vvetfelting.v The fibrous pulp is suspended in watertoa'consistency of usuallyl about 1%,

and resin size andalum are addedto giveV water resistance to ',the': dry board.v Waxes may also. beuse'dfor sizing; The fibers are'then deposited onva wirescren veitherrby gravityor by suction' by allowing the Water to bev drawn away through thedepos'ited 'iibrous mass. f The wet felted mass tween fwool" felts or.`\`,vire screens, to eliminate all Vthe.A Water possible van'd :produce a compacted feltedboard which whendried Will be approximately 1/2'thick'.v

After `all'possible waterV has been pressed out and'beforethewetmat is dried, a material is appliedto'the ftop' surface 'in an amount that on penetrating'ithe wet-mat Will be'suicient toV neutralize theeffect' of the size to a depth that will give the desired degree of absorption on the dry board.` This'depth is generally approximately 1,32 in'ch'.V "When the 'mat isdry, this, and onlyV this, portion of the mat is abSOrptive, while the l remainder will ber-well sized and water resistant. We have discovered that an aldehyde,` such as formaldehydes or'furfural-When incorporated Withithe surfaceof'thelining` will act as an antistickingagent We have yfurther discoveredthatVV this typeofmaterialrnay be added as one ofther Y :ifa .ingredients 'o'ffth'e above Wet mat coating and still be effective after it is dried.

In one simple and economic operation, in addition to those of the regular process of insulation board manufacture, this coating material is applied to the Wet mat and the resultant product is a new and improved form lining material.

The coating material is composed of a caustic material such as sodium hydroxide which acts to neutralize the size and an aldehyde, such for example as furfural, to act as an anti-sticking agent.

In order to prevent a reaction between the caustic and furfural, cold water must be used in preparing the coating and when using a caustic material such as sodium hydroxide, the ratio of caustic to furfural should not exceed one to ve.

The following is an example of a suitable coating composition:

Parts Water' 300 Furfural 100 NaOH 20 The caustic is dissolved in the cold water and the furfural is added with sufficient agitation until it becomes emulsied in the solution, after whichkthe resulting emulsion may be applied to the mat surface.

In order to form a more stable emulsion, an emulsifying or wetting agent may be used. There are a large number of these now known and o may use:

Parts Water 300 Furfural 50 NaOH 12 Wetting agent 8 The wetting agent cannot be completely substituted for the caustic to give absorptiv'e properties to the lining surface because the resultant mat will not meet the government specifications for form lining absorption. The specifications require that a lining surface of 16 square inches absorb between 6 to 16 grams of saturated lime water during the rst 15 minutes, 15 to 26 grams in 60 minutes, and 18 to 29 grams in 120 minutes; If a wetting agent alone is used, almost all of the absorption is obtained in the rst few minutes so that for l minutes the results are on the high side and practically no water is absorbed thereafter, at least not enough to meet the specifications. When caustic alone or a com-` bination of caustic and the wetting agent is used, the caustic in the dried board dissolves in the absorbed water and tends to continue to neutralize the size so that the absorption is extended over a longer period and may be regulated to meet government specifications.

One of the wetting agents which we have found to be particularly well suited is a sulfonated hydrocarbon. Y.

The method of application of the modifying material is substantially as follows (referring to Fig. 1): A suitably sized cellulosic fiber furnish flows from stock-chest 3 through controlvalve 4 into the Oliver type of board-former 5, upon the perforated or screen-covered drum 6 of which the board 'I is initially formed.':..The

freshly formed board then passes over the usual supporting belt 8 which travels on supporting rolls 9, being kept under suitable tension by passing over rollers I0 and I I. The belt is waterpermeable, usually being made of some sort of felt, so that it may absorb the Water from the board. The extraction of Water from the freshly formed board is further aided by the use of the usual pressroll, such as roll I2.` Usually, after passing such a roll, there remains about 50% to 70% of water in the board. After passing this roll the composition of the present invention is applied to the board, as, for example, through a hopper I3 into which the composition is fed from a source of supply, as the storage tank I4, the ow being controlled by a valve I5 in pipe I6. The material will thus form a pool directly ahead of the spreading roll II, which applies it evenly to the surface of the Wet board. Thereafter the board may be cut by means of a traveling knife I8, and the lengths thus severed may passontoan accelerated section of a conveyor I9 and thence, through the intermediate tipple 20, into a multi-deck drier 2| in which the boards are'dried, being discharged from the,4 latter through tipple 22 to be received on table, 23. During the drying the sodium hydroxide: contained in the coating composition will combine with the sizing material to form a sort ofi soap, whereby the. sizing eiect is destroyed, thus:

.making the outer portions of the board much'.

into consideration that the illustration is more or less diagrammatical, and that there really is: no sharp line of demarcation between the desized and the sized portions of the board.

It will of course be obvious to those skilled in this art that the mechanical equipment employed may vary considerably from that hereinabove' described, and that the main feature to be kept in mind is the application of the aldehyde emulsion or solution to the board at a stage in which it still contains considerable free water.

We claim:

1. Process of producing a size-containing ber board suitable for the lining of concrete forms, which comprises forming a wet mat from sized lignocellulosic fibers and applying to the still wet surface of said mat on the side intended to contact the Wet concrete a Ycomposition consisting of a dilute aqueous solution of sodium hydroxide and an aldehyde fromthe group consisting of formaldehyde andfurfural in which the sodium hydroxide is not more than about one-fifth the weight of the aldehyde, and drying the mat.

2. Process of producing a size-containing ber board suitable for the lining of concrete forms, which comprises forming a wet mat from sized lignocellulosic fibers and applying to the still wet surface of said mat on the side intended to contact the wet concrete a composition consisting of a dilute aqueous solution of sodium hydroxide and formaldehyde, in which the sodium hydroxide is not more than about one-ith the weight of the formaldehyde and drying the mat.

3. Process of producing a size-containing nber board suitable for the lining of concrete forms, which comprises forming a Wet mat from sized lignocellulosic bers and applying to the still wet surface of said mat on the side intended to contact the wet concrete a composition consisting of a dilute aqueous solution of sodium hydroxide, furfural and a wetting agent, in which the sodium hydroxide is not more than about one-fifth the Weight of the furfural and drying the mat.

4. Process of producing a iiber board suitable for the lining of concrete forms, which comprises forrning a wet mat from sized lignocellulcsic fibers, and applying to the still Wet surface of said mat on the side intended to contact the wet concrete a composition comprising about 20 parts of sodium hydroxide and about 100 parts of furfural dispersed in about 300 parts of water.

5. Process of producing a fiber board suitable for the lining of concrete forms, which comprises forming a wet mat from sized lignocellulosic fibers and applying to the still wet surface of said mat on the side intended to contact the wet concrete a composition comprising about 50 parts of furfural, about 12 parts of sodium hydroxide, and about 8 parts of a wetting agent dispersed in about 300 parts of water.

6. A relatively rigid concrete-form lining material comprising ber board having its fibers coated with a sizing material throughout the body of the board except on the side intended to contact the wet concrete, on which side the sizing material has been destroyed to a depth of about 33e of an inch, whereby the said board will be capable of absorbing Water from wet concrete in the following proportions: each 16 square inches thereof will absorb between 6 and 16 grams of saturated lime water during the i'lrst l5 minutes, 15 to 26 grams in 60 minutes, and 18 to 29 grams in 120 minutes.

7. The concrete-form lining material as defined in claim 6, in which the side of the board in which the sizing material has been destroyed contains fibers carrying an aldehyde.

8. The concrete-form lining material as denned in claim 7 in which the aldehyde is furfural.

9. The concrete-form lining material as dened in claim 7 in which the aldehyde is formaldehyde.

10. Process of rendering a sized wood-fiber board suitable for use as a non-sticking concrete-form material which comprises applying to said board, during a stage in its manufacture where it still contains free moisture, a sufficient amount of an alkaline-reacting emulsion of furfural, containing about one-fth as much of an alkali as furfural, to desize said board to a depth of about g3g and to leave a film of iurfural on the fibers of the board in the desized portions of the latter.

11. The process as defined in claim 10 in which the emulsion is one of furfural in a solution of sodium hydroxide, and there being about five times as much furfural as sodium hydroxide.

12. Process as deiined in claim 10 in which the emulsion is one of urfural in a solution of sodium hydroxide also containing a wetting agent not adversely affected by said sodium hydroxide, and there being about five times as much iurfural as sodium hydroxide.

13. The process of producing a readily separable concrete form liner which comprises forming a wet mat from conventionally sized lignocellulosic bers, altering the chemical structure of the iibers and destroying the size thereon in about the surface layer of said wet mat to a depth of about 3-2 of an inch by the action or" an alkaline reacting solution of an aldehyde from the group consisting of formaldehyde and furfural, and then drying said thus treated mat, the ratio of alkali to aldehyde in said solution being about as 1:5.

ORCUTT W. FROST. JAMES H. CONOVER.

REFERENCES CITEB The following references are of record in the nie of this patent:

UNITED STATES PATENTS Number Name Date Re. 11,811 Hall Mar. 6, 1900 52,788 Gwynn Feb. 20, 1866 1,004,844 .Bennett Oct. 3, 1911 1,637,321 Johnson July 26, 1927 1,665,236 Trickey Apr. 10, 1928 1,981,405 Wrede Nov. 20, 1934 1,996,487 Patrick Apr. 2, 1935 2,010,635 Kantorowicz Aug. 6, 1935 2,176,981 Smith et al. Oct. 24, 1939 2,296,553 Heritage et al Sept. 22, 1942 2,310,400 Crane et al Feb. 9, 1943 2,364,772 Bohm Dec. 12, 1944 2,409,629 Heritage Oct. 22, 1946 2,409,630 Heritage et al Oct. 22, 1946 2,432,002 Frederick et al Dec. 2, 1947 yFOREIGN PATENTS Number Country Date 528,030 Germany June 24, 1931 meister, third edition (1941), p. 296 (John Wiley Ez Sons) 

